Powder for dusting patterns.



FRANZ DAMHORST, AUGUST KEMPER, AND ERNST 'UTKE, OFBERLIN, GERMANY.

P OWDER FOR DUSTI NG PATTERNS.

Specification of Letters Patent.

Patented May 8,1906.

Application filed June 29,1905- Serial No. 267,618.

To alt whom it may concern:

Be it known that we, FRANZ DAMHORST and AUGUST KEMPER, manufacturers,and ERNST UT'KE, molder, subjects of the German Emperor, residing atBerlin, in the Empire of Germany, have invented new and usefulImprovements in Powder for Dusting Patterns, of which'the following is aspecification.

In the preparation of molds from patterns, especially such patterns asserve for the production of finer castings, lycopodium powder hashitherto been regularly employed for powdering the pattern. Thelycopodium forms between the pattern and the mold a separating layerwhich renders impossible direct contact between the molding-sand and thepattern, the clinging of the pattern to the mold being intended to beconsequently prevented. Practice has nevertheless shown that in spite ofthe use of very expensive lycopodium unevennesses and raw places appearon the surfaces of the castings. These unevennesses on the casting areprincipally to be attributed to the fact that the lycopodium on accountof its slight specific weight lacks the capacity of clingingsulficiently to the pattern, so that the layer of lycopodium ispartially removed from the pattern when the sand is sieved in andpartially collects together, results which naturally cause the surfaceof the mold itself to become uneven and produce unclean castings. Theslight capacity which the lycopodium possesses to cling to the patternmakes itself particularly unpleasantly noticeable when the pattern hasfairly large vertical surfaces. In the case of such patterns it ispossible to cause the lycopodium to cling to a certain extent only bypressing by hand molding-sand against the surfaces of the pattern beforesifting in sand, an expedient which requires time and work while,however, nevertheless it cannot affect the maintenance of a uniformintermediate layer; but, on the contrary, by this expedient adisarrangement of the lycopodium layer in itself is caused to take placeand a non-uniform distribution of the same on the pattern is broughtabout. Further, the lycopodium has a disadvantage in that the parts ofthe same clinging to the mold burn and form ashes when the mold isdried, whereby the surface of the mold is made rough, which naturallyhas as a consequence the production of a correspondingly rough surfaceon the casting.

According to the present invention the facilitation of the removal ofthe pattern from the mold is effected not by the intermediate insertionbetween pattern and mold of a layer consisting of specifically lighterorganic materials, but by employing a mineral powder which on the onehand renders it possible to coat the pattern with an exceedingly finelayer capable of clinging well and on the other hand has the effect thata layer of gas or steam is formed between the pattern and the mold bythe powder touching the moist molding-sand, which layer brings about theseparation of the pattern from the mold. As

an example of such pattern-powder may be mentioned calcium carbid.

If a Cpattern after having been previously spraye with petroleum issprayed with powdered carbid, acetylene-gas is generated, even atordinary temperatures, on the moist molding-sand touching the carbid,which gas forms a kind of separating layer between the pattern and themold and renders it possible to remove the pattern readily without thedanger of damaging the mold. In this case the previous spraying of thepattern with pctroleum is of importance on account of the fact that thelatter retards the combination of water with the carbid, so that thegeneration of gas is slow and lasts until the ramming of the mold iscomplete. The use of carbid as a pattern-powder has also the advantagethat on the one hand it is much cheaper than lycopodium, while on theother hand also it clings to the pattern in such a manner that themolding-sand can be sifted in and rammed without a disarrangement of theparticles of the powder being thereby brought about. In consequence ofthis circumstance and of the layer of gas appearing as a separatinglayer the mold, and consequently also the casting, has an absolutelysmooth surface.

If pulverized quicklime be employed as the pattern-powder, which, as iswell known, becomes converted into hydrate of lime on coming intocontact with water and which by this conversion produces a considerabledevelopment of heat, in consequence of this heat development avaporization of the particles of moisture in the molding-sand notchemically bound takes place, so that a layer of steam is formed betweenthe mold and the pattern or the layer of lime covering the latter, whichlayer of steam in the same manner as the gas layer in thecase'of thecar- In testimony whereof We havesig'ned our 10 bid acts as a separatinglayer between the names to this specification in the presence ofpatternand the mold and excludes the dan l twosubsoribing Witnesses.

ger of the pattern clinging to the mold When FRANZ DANEHORST. 5 it isremoved. AUGUST KEMPER.

What We claim as our invention, and de- ERNST UTKE. sire to secure byLetters Patent, is- Witnesses:

Powder for dusting patterns, containing HENRY HASPER,

powdery pulverized calcium carbid. WOLDEMAR HAUPT.

